/*
 * jdmarker.c
 *
 * Copyright (C) 1991-1995, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains routines to decode JPEG datastream markers.
 * Most of the complexity arises from our desire to support input
 * suspension: if not all of the data for a marker is available,
 * we must exit back to the application.  On resumption, we reprocess
 * the marker.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


typedef enum {          /* JPEG marker codes */
    M_SOF0  = 0xc0,
    M_SOF1  = 0xc1,
    M_SOF2  = 0xc2,
    M_SOF3  = 0xc3,

    M_SOF5  = 0xc5,
    M_SOF6  = 0xc6,
    M_SOF7  = 0xc7,

    M_JPG   = 0xc8,
    M_SOF9  = 0xc9,
    M_SOF10 = 0xca,
    M_SOF11 = 0xcb,

    M_SOF13 = 0xcd,
    M_SOF14 = 0xce,
    M_SOF15 = 0xcf,

    M_DHT   = 0xc4,

    M_DAC   = 0xcc,

    M_RST0  = 0xd0,
    M_RST1  = 0xd1,
    M_RST2  = 0xd2,
    M_RST3  = 0xd3,
    M_RST4  = 0xd4,
    M_RST5  = 0xd5,
    M_RST6  = 0xd6,
    M_RST7  = 0xd7,

    M_SOI   = 0xd8,
    M_EOI   = 0xd9,
    M_SOS   = 0xda,
    M_DQT   = 0xdb,
    M_DNL   = 0xdc,
    M_DRI   = 0xdd,
    M_DHP   = 0xde,
    M_EXP   = 0xdf,

    M_APP0  = 0xe0,
    M_APP1  = 0xe1,
    M_APP2  = 0xe2,
    M_APP3  = 0xe3,
    M_APP4  = 0xe4,
    M_APP5  = 0xe5,
    M_APP6  = 0xe6,
    M_APP7  = 0xe7,
    M_APP8  = 0xe8,
    M_APP9  = 0xe9,
    M_APP10 = 0xea,
    M_APP11 = 0xeb,
    M_APP12 = 0xec,
    M_APP13 = 0xed,
    M_APP14 = 0xee,
    M_APP15 = 0xef,

    M_JPG0  = 0xf0,
    M_JPG13 = 0xfd,
    M_COM   = 0xfe,

    M_TEM   = 0x01,

    M_ERROR = 0x100
} JPEG_MARKER;


/*
 * Macros for fetching data from the data source module.
 *
 * At all times, cinfo->src->next_input_byte and ->bytes_in_buffer reflect
 * the current restart point; we update them only when we have reached a
 * suitable place to restart if a suspension occurs.
 */

/* Declare and initialize local copies of input pointer/count */
#define INPUT_VARS( cinfo )  \
    struct jpeg_source_mgr * datasrc = ( cinfo )->src;  \
    const JOCTET * next_input_byte = datasrc->next_input_byte;  \
    size_t bytes_in_buffer = datasrc->bytes_in_buffer

/* Unload the local copies --- do this only at a restart boundary */
#define INPUT_SYNC( cinfo )  \
    ( datasrc->next_input_byte = next_input_byte,  \
      datasrc->bytes_in_buffer = bytes_in_buffer )

/* Reload the local copies --- seldom used except in MAKE_BYTE_AVAIL */
#define INPUT_RELOAD( cinfo )  \
    ( next_input_byte = datasrc->next_input_byte,  \
      bytes_in_buffer = datasrc->bytes_in_buffer )

/* Internal macro for INPUT_BYTE and INPUT_2BYTES: make a byte available.
 * Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
 * but we must reload the local copies after a successful fill.
 */
#define MAKE_BYTE_AVAIL( cinfo, action )  \
    if ( bytes_in_buffer == 0 ) {  \
        if ( !( *datasrc->fill_input_buffer )( cinfo ) )  \
        { action; }  \
        INPUT_RELOAD( cinfo );  \
    }  \
    bytes_in_buffer--

/* Read a byte into variable V.
 * If must suspend, take the specified action (typically "return FALSE").
 */
#define INPUT_BYTE( cinfo, V, action )  \
    MAKESTMT( MAKE_BYTE_AVAIL( cinfo, action ); \
              V = GETJOCTET( *next_input_byte++ ); )

/* As above, but read two bytes interpreted as an unsigned 16-bit integer.
 * V should be declared unsigned int or perhaps INT32.
 */
#define INPUT_2BYTES( cinfo, V, action )  \
    MAKESTMT( MAKE_BYTE_AVAIL( cinfo, action ); \
              V = ( (unsigned int) GETJOCTET( *next_input_byte++ ) ) << 8; \
              MAKE_BYTE_AVAIL( cinfo, action ); \
              V += GETJOCTET( *next_input_byte++ ); )


/*
 * Routines to process JPEG markers.
 *
 * Entry condition: JPEG marker itself has been read and its code saved
 *   in cinfo->unread_marker; input restart point is just after the marker.
 *
 * Exit: if return TRUE, have read and processed any parameters, and have
 *   updated the restart point to point after the parameters.
 *   If return FALSE, was forced to suspend before reaching end of
 *   marker parameters; restart point has not been moved.  Same routine
 *   will be called again after application supplies more input data.
 *
 * This approach to suspension assumes that all of a marker's parameters can
 * fit into a single input bufferload.  This should hold for "normal"
 * markers.  Some COM/APPn markers might have large parameter segments,
 * but we use skip_input_data to get past those, and thereby put the problem
 * on the source manager's shoulders.
 *
 * Note that we don't bother to avoid duplicate trace messages if a
 * suspension occurs within marker parameters.  Other side effects
 * require more care.
 */


LOCAL boolean
get_soi( j_decompress_ptr cinfo ) {
/* Process an SOI marker */
    int i;

    TRACEMS( cinfo, 1, JTRC_SOI );

    if ( cinfo->marker->saw_SOI ) {
        ERREXIT( cinfo, JERR_SOI_DUPLICATE );
    }

    /* Reset all parameters that are defined to be reset by SOI */

    for ( i = 0; i < NUM_ARITH_TBLS; i++ ) {
        cinfo->arith_dc_L[i] = 0;
        cinfo->arith_dc_U[i] = 1;
        cinfo->arith_ac_K[i] = 5;
    }
    cinfo->restart_interval = 0;

    /* Set initial assumptions for colorspace etc */

    cinfo->jpeg_color_space = JCS_UNKNOWN;
    cinfo->CCIR601_sampling = FALSE;/* Assume non-CCIR sampling??? */

    cinfo->saw_JFIF_marker = FALSE;
    cinfo->density_unit = 0;/* set default JFIF APP0 values */
    cinfo->X_density = 1;
    cinfo->Y_density = 1;
    cinfo->saw_Adobe_marker = FALSE;
    cinfo->Adobe_transform = 0;

    cinfo->marker->saw_SOI = TRUE;

    return TRUE;
}


LOCAL boolean
get_sof( j_decompress_ptr cinfo, boolean is_prog, boolean is_arith ) {
/* Process a SOFn marker */
    INT32 length;
    int c, ci;
    jpeg_component_info * compptr;
    INPUT_VARS( cinfo );

    cinfo->progressive_mode = is_prog;
    cinfo->arith_code = is_arith;

    INPUT_2BYTES( cinfo, length, return FALSE );

    INPUT_BYTE( cinfo, cinfo->data_precision, return FALSE );
    INPUT_2BYTES( cinfo, cinfo->image_height, return FALSE );
    INPUT_2BYTES( cinfo, cinfo->image_width, return FALSE );
    INPUT_BYTE( cinfo, cinfo->num_components, return FALSE );

    length -= 8;

    TRACEMS4( cinfo, 1, JTRC_SOF, cinfo->unread_marker,
              (int) cinfo->image_width, (int) cinfo->image_height,
              cinfo->num_components );

    if ( cinfo->marker->saw_SOF ) {
        ERREXIT( cinfo, JERR_SOF_DUPLICATE );
    }

    /* We don't support files in which the image height is initially specified */
    /* as 0 and is later redefined by DNL.  As long as we have to check that,  */
    /* might as well have a general sanity check. */
    if ( ( cinfo->image_height <= 0 ) || ( cinfo->image_width <= 0 )
        || ( cinfo->num_components <= 0 ) ) {
        ERREXIT( cinfo, JERR_EMPTY_IMAGE );
    }

    if ( length != ( cinfo->num_components * 3 ) ) {
        ERREXIT( cinfo, JERR_BAD_LENGTH );
    }

    if ( cinfo->comp_info == NULL ) {/* do only once, even if suspend */
        cinfo->comp_info = (jpeg_component_info *) ( *cinfo->mem->alloc_small )
                           ( (j_common_ptr) cinfo, JPOOL_IMAGE,
                            cinfo->num_components * SIZEOF( jpeg_component_info ) );
    }

    for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
          ci++, compptr++ ) {
        compptr->component_index = ci;
        INPUT_BYTE( cinfo, compptr->component_id, return FALSE );
        INPUT_BYTE( cinfo, c, return FALSE );
        compptr->h_samp_factor = ( c >> 4 ) & 15;
        compptr->v_samp_factor = ( c     ) & 15;
        INPUT_BYTE( cinfo, compptr->quant_tbl_no, return FALSE );

        TRACEMS4( cinfo, 1, JTRC_SOF_COMPONENT,
                  compptr->component_id, compptr->h_samp_factor,
                  compptr->v_samp_factor, compptr->quant_tbl_no );
    }

    cinfo->marker->saw_SOF = TRUE;

    INPUT_SYNC( cinfo );
    return TRUE;
}


LOCAL boolean
get_sos( j_decompress_ptr cinfo ) {
/* Process a SOS marker */
    INT32 length;
    int i, ci, n, c, cc;
    jpeg_component_info * compptr;
    INPUT_VARS( cinfo );

    if ( !cinfo->marker->saw_SOF ) {
        ERREXIT( cinfo, JERR_SOS_NO_SOF );
    }

    INPUT_2BYTES( cinfo, length, return FALSE );

    INPUT_BYTE( cinfo, n, return FALSE );/* Number of components */

    if ( ( length != ( n * 2 + 6 ) || n < 1 ) || ( n > MAX_COMPS_IN_SCAN ) ) {
        ERREXIT( cinfo, JERR_BAD_LENGTH );
    }

    TRACEMS1( cinfo, 1, JTRC_SOS, n );

    cinfo->comps_in_scan = n;

    /* Collect the component-spec parameters */

    for ( i = 0; i < n; i++ ) {
        INPUT_BYTE( cinfo, cc, return FALSE );
        INPUT_BYTE( cinfo, c, return FALSE );

        for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
              ci++, compptr++ ) {
            if ( cc == compptr->component_id ) {
                goto id_found;
            }
        }

        ERREXIT1( cinfo, JERR_BAD_COMPONENT_ID, cc );

id_found:

        cinfo->cur_comp_info[i] = compptr;
        compptr->dc_tbl_no = ( c >> 4 ) & 15;
        compptr->ac_tbl_no = ( c     ) & 15;

        TRACEMS3( cinfo, 1, JTRC_SOS_COMPONENT, cc,
                  compptr->dc_tbl_no, compptr->ac_tbl_no );
    }

    /* Collect the additional scan parameters Ss, Se, Ah/Al. */
    INPUT_BYTE( cinfo, c, return FALSE );
    cinfo->Ss = c;
    INPUT_BYTE( cinfo, c, return FALSE );
    cinfo->Se = c;
    INPUT_BYTE( cinfo, c, return FALSE );
    cinfo->Ah = ( c >> 4 ) & 15;
    cinfo->Al = ( c     ) & 15;

    TRACEMS4( cinfo, 1, JTRC_SOS_PARAMS, cinfo->Ss, cinfo->Se,
              cinfo->Ah, cinfo->Al );

    /* Prepare to scan data & restart markers */
    cinfo->marker->next_restart_num = 0;

    /* Count another SOS marker */
    cinfo->input_scan_number++;

    INPUT_SYNC( cinfo );
    return TRUE;
}


METHODDEF boolean
get_app0( j_decompress_ptr cinfo ) {
/* Process an APP0 marker */
#define JFIF_LEN 14
    INT32 length;
    UINT8 b[JFIF_LEN];
    int buffp;
    INPUT_VARS( cinfo );

    INPUT_2BYTES( cinfo, length, return FALSE );
    length -= 2;

    /* See if a JFIF APP0 marker is present */

    if ( length >= JFIF_LEN ) {
        for ( buffp = 0; buffp < JFIF_LEN; buffp++ ) {
            INPUT_BYTE( cinfo, b[buffp], return FALSE );
        }
        length -= JFIF_LEN;

        if ( ( b[0] == 0x4A ) && ( b[1] == 0x46 ) && ( b[2] == 0x49 ) && ( b[3] == 0x46 ) && ( b[4] == 0 ) ) {
            /* Found JFIF APP0 marker: check version */
            /* Major version must be 1, anything else signals an incompatible change.
             * We used to treat this as an error, but now it's a nonfatal warning,
             * because some bozo at Hijaak couldn't read the spec.
             * Minor version should be 0..2, but process anyway if newer.
             */
            if ( b[5] != 1 ) {
                WARNMS2( cinfo, JWRN_JFIF_MAJOR, b[5], b[6] );
            } else if ( b[6] > 2 ) {
                TRACEMS2( cinfo, 1, JTRC_JFIF_MINOR, b[5], b[6] );
            }
            /* Save info */
            cinfo->saw_JFIF_marker = TRUE;
            cinfo->density_unit = b[7];
            cinfo->X_density = ( b[8] << 8 ) + b[9];
            cinfo->Y_density = ( b[10] << 8 ) + b[11];
            TRACEMS3( cinfo, 1, JTRC_JFIF,
                      cinfo->X_density, cinfo->Y_density, cinfo->density_unit );
            if ( b[12] | b[13] ) {
                TRACEMS2( cinfo, 1, JTRC_JFIF_THUMBNAIL, b[12], b[13] );
            }
            if ( length != ( (INT32) b[12] * (INT32) b[13] * (INT32) 3 ) ) {
                TRACEMS1( cinfo, 1, JTRC_JFIF_BADTHUMBNAILSIZE, (int) length );
            }
        } else {
            /* Start of APP0 does not match "JFIF" */
            TRACEMS1( cinfo, 1, JTRC_APP0, (int) length + JFIF_LEN );
        }
    } else {
        /* Too short to be JFIF marker */
        TRACEMS1( cinfo, 1, JTRC_APP0, (int) length );
    }

    INPUT_SYNC( cinfo );
    if ( length > 0 ) { /* skip any remaining data -- could be lots */
        ( *cinfo->src->skip_input_data )( cinfo, (long) length );
    }

    return TRUE;
}


METHODDEF boolean
get_app14( j_decompress_ptr cinfo ) {
/* Process an APP14 marker */
#define ADOBE_LEN 12
    INT32 length;
    UINT8 b[ADOBE_LEN];
    int buffp;
    unsigned int version, flags0, flags1, transform;
    INPUT_VARS( cinfo );

    INPUT_2BYTES( cinfo, length, return FALSE );
    length -= 2;

    /* See if an Adobe APP14 marker is present */

    if ( length >= ADOBE_LEN ) {
        for ( buffp = 0; buffp < ADOBE_LEN; buffp++ ) {
            INPUT_BYTE( cinfo, b[buffp], return FALSE );
        }
        length -= ADOBE_LEN;

        if ( ( b[0] == 0x41 ) && ( b[1] == 0x64 ) && ( b[2] == 0x6F ) && ( b[3] == 0x62 ) && ( b[4] == 0x65 ) ) {
            /* Found Adobe APP14 marker */
            version = ( b[5] << 8 ) + b[6];
            flags0 = ( b[7] << 8 ) + b[8];
            flags1 = ( b[9] << 8 ) + b[10];
            transform = b[11];
            TRACEMS4( cinfo, 1, JTRC_ADOBE, version, flags0, flags1, transform );
            cinfo->saw_Adobe_marker = TRUE;
            cinfo->Adobe_transform = (UINT8) transform;
        } else {
            /* Start of APP14 does not match "Adobe" */
            TRACEMS1( cinfo, 1, JTRC_APP14, (int) length + ADOBE_LEN );
        }
    } else {
        /* Too short to be Adobe marker */
        TRACEMS1( cinfo, 1, JTRC_APP14, (int) length );
    }

    INPUT_SYNC( cinfo );
    if ( length > 0 ) { /* skip any remaining data -- could be lots */
        ( *cinfo->src->skip_input_data )( cinfo, (long) length );
    }

    return TRUE;
}


LOCAL boolean
get_dac( j_decompress_ptr cinfo ) {
/* Process a DAC marker */
    INT32 length;
    int index, val;
    INPUT_VARS( cinfo );

    INPUT_2BYTES( cinfo, length, return FALSE );
    length -= 2;

    while ( length > 0 ) {
        INPUT_BYTE( cinfo, index, return FALSE );

        INPUT_BYTE( cinfo, val, return FALSE );

        length -= 2;

        TRACEMS2( cinfo, 1, JTRC_DAC, index, val );

        if ( ( index < 0 ) || ( index >= ( 2 * NUM_ARITH_TBLS ) ) ) {
            ERREXIT1( cinfo, JERR_DAC_INDEX, index );
        }

        if ( index >= NUM_ARITH_TBLS ) {/* define AC table */
            cinfo->arith_ac_K[index - NUM_ARITH_TBLS] = (UINT8) val;
        } else {        /* define DC table */
            cinfo->arith_dc_L[index] = (UINT8) ( val & 0x0F );
            cinfo->arith_dc_U[index] = (UINT8) ( val >> 4 );
            if ( cinfo->arith_dc_L[index] > cinfo->arith_dc_U[index] ) {
                ERREXIT1( cinfo, JERR_DAC_VALUE, val );
            }
        }
    }

    INPUT_SYNC( cinfo );
    return TRUE;
}


LOCAL boolean
get_dht( j_decompress_ptr cinfo ) {
/* Process a DHT marker */
    INT32 length;
    UINT8 bits[17];
    UINT8 huffval[256];
    int i, index, count;
    JHUFF_TBL ** htblptr;
    INPUT_VARS( cinfo );

    INPUT_2BYTES( cinfo, length, return FALSE );
    length -= 2;

    while ( length > 0 ) {
        INPUT_BYTE( cinfo, index, return FALSE );

        TRACEMS1( cinfo, 1, JTRC_DHT, index );

        bits[0] = 0;
        count = 0;
        for ( i = 1; i <= 16; i++ ) {
            INPUT_BYTE( cinfo, bits[i], return FALSE );
            count += bits[i];
        }

        length -= 1 + 16;

        TRACEMS8( cinfo, 2, JTRC_HUFFBITS,
                  bits[1], bits[2], bits[3], bits[4],
                  bits[5], bits[6], bits[7], bits[8] );
        TRACEMS8( cinfo, 2, JTRC_HUFFBITS,
                  bits[9], bits[10], bits[11], bits[12],
                  bits[13], bits[14], bits[15], bits[16] );

        if ( ( count > 256 ) || ( ( (INT32) count ) > length ) ) {
            ERREXIT( cinfo, JERR_DHT_COUNTS );
        }

        for ( i = 0; i < count; i++ ) {
            INPUT_BYTE( cinfo, huffval[i], return FALSE );
        }

        length -= count;

        if ( index & 0x10 ) {/* AC table definition */
            index -= 0x10;
            htblptr = &cinfo->ac_huff_tbl_ptrs[index];
        } else {        /* DC table definition */
            htblptr = &cinfo->dc_huff_tbl_ptrs[index];
        }

        if ( ( index < 0 ) || ( index >= NUM_HUFF_TBLS ) ) {
            ERREXIT1( cinfo, JERR_DHT_INDEX, index );
        }

        if ( *htblptr == NULL ) {
            *htblptr = jpeg_alloc_huff_table( (j_common_ptr) cinfo );
        }

        MEMCOPY( ( *htblptr )->bits, bits, SIZEOF( ( *htblptr )->bits ) );
        MEMCOPY( ( *htblptr )->huffval, huffval, SIZEOF( ( *htblptr )->huffval ) );
    }

    INPUT_SYNC( cinfo );
    return TRUE;
}


LOCAL boolean
get_dqt( j_decompress_ptr cinfo ) {
/* Process a DQT marker */
    INT32 length;
    int n, i, prec;
    unsigned int tmp;
    JQUANT_TBL * quant_ptr;
    INPUT_VARS( cinfo );

    INPUT_2BYTES( cinfo, length, return FALSE );
    length -= 2;

    while ( length > 0 ) {
        INPUT_BYTE( cinfo, n, return FALSE );

        prec = n >> 4;
        n &= 0x0F;

        TRACEMS2( cinfo, 1, JTRC_DQT, n, prec );

        if ( n >= NUM_QUANT_TBLS ) {
            ERREXIT1( cinfo, JERR_DQT_INDEX, n );
        }

        if ( cinfo->quant_tbl_ptrs[n] == NULL ) {
            cinfo->quant_tbl_ptrs[n] = jpeg_alloc_quant_table( (j_common_ptr) cinfo );
        }
        quant_ptr = cinfo->quant_tbl_ptrs[n];

        for ( i = 0; i < DCTSIZE2; i++ ) {
            if ( prec ) {
                INPUT_2BYTES( cinfo, tmp, return FALSE );
            } else {
                INPUT_BYTE( cinfo, tmp, return FALSE );
            }
            quant_ptr->quantval[i] = (UINT16) tmp;
        }

        for ( i = 0; i < DCTSIZE2; i += 8 ) {
            TRACEMS8( cinfo, 2, JTRC_QUANTVALS,
                      quant_ptr->quantval[i  ], quant_ptr->quantval[i + 1],
                      quant_ptr->quantval[i + 2], quant_ptr->quantval[i + 3],
                      quant_ptr->quantval[i + 4], quant_ptr->quantval[i + 5],
                      quant_ptr->quantval[i + 6], quant_ptr->quantval[i + 7] );
        }

        length -= DCTSIZE2 + 1;
        if ( prec ) {
            length -= DCTSIZE2;
        }
    }

    INPUT_SYNC( cinfo );
    return TRUE;
}


LOCAL boolean
get_dri( j_decompress_ptr cinfo ) {
/* Process a DRI marker */
    INT32 length;
    unsigned int tmp;
    INPUT_VARS( cinfo );

    INPUT_2BYTES( cinfo, length, return FALSE );

    if ( length != 4 ) {
        ERREXIT( cinfo, JERR_BAD_LENGTH );
    }

    INPUT_2BYTES( cinfo, tmp, return FALSE );

    TRACEMS1( cinfo, 1, JTRC_DRI, tmp );

    cinfo->restart_interval = tmp;

    INPUT_SYNC( cinfo );
    return TRUE;
}


METHODDEF boolean
skip_variable( j_decompress_ptr cinfo ) {
/* Skip over an unknown or uninteresting variable-length marker */
    INT32 length;
    INPUT_VARS( cinfo );

    INPUT_2BYTES( cinfo, length, return FALSE );

    TRACEMS2( cinfo, 1, JTRC_MISC_MARKER, cinfo->unread_marker, (int) length );

    INPUT_SYNC( cinfo );    /* do before skip_input_data */
    ( *cinfo->src->skip_input_data )( cinfo, (long) length - 2L );

    return TRUE;
}


/*
 * Find the next JPEG marker, save it in cinfo->unread_marker.
 * Returns FALSE if had to suspend before reaching a marker;
 * in that case cinfo->unread_marker is unchanged.
 *
 * Note that the result might not be a valid marker code,
 * but it will never be 0 or FF.
 */

LOCAL boolean
next_marker( j_decompress_ptr cinfo ) {
    int c;
    INPUT_VARS( cinfo );

    for (;; ) {
        INPUT_BYTE( cinfo, c, return FALSE );
        /* Skip any non-FF bytes.
         * This may look a bit inefficient, but it will not occur in a valid file.
         * We sync after each discarded byte so that a suspending data source
         * can discard the byte from its buffer.
         */
        while ( c != 0xFF ) {
            cinfo->marker->discarded_bytes++;

            INPUT_SYNC( cinfo );
            INPUT_BYTE( cinfo, c, return FALSE );
        }
        /* This loop swallows any duplicate FF bytes.  Extra FFs are legal as
         * pad bytes, so don't count them in discarded_bytes.  We assume there
         * will not be so many consecutive FF bytes as to overflow a suspending
         * data source's input buffer.
         */
        do {
            INPUT_BYTE( cinfo, c, return FALSE );
        } while ( c == 0xFF );
        if ( c != 0 ) {
            break;
        }               /* found a valid marker, exit loop */
        /* Reach here if we found a stuffed-zero data sequence (FF/00).
         * Discard it and loop back to try again.
         */
        cinfo->marker->discarded_bytes += 2;
        INPUT_SYNC( cinfo );
    }

    if ( cinfo->marker->discarded_bytes != 0 ) {
        WARNMS2( cinfo, JWRN_EXTRANEOUS_DATA, cinfo->marker->discarded_bytes, c );
        cinfo->marker->discarded_bytes = 0;
    }

    cinfo->unread_marker = c;

    INPUT_SYNC( cinfo );
    return TRUE;
}


LOCAL boolean
first_marker( j_decompress_ptr cinfo ) {
/* Like next_marker, but used to obtain the initial SOI marker. */
/* For this marker, we do not allow preceding garbage or fill; otherwise,
 * we might well scan an entire input file before realizing it ain't JPEG.
 * If an application wants to process non-JFIF files, it must seek to the
 * SOI before calling the JPEG library.
 */
    int c, c2;
    INPUT_VARS( cinfo );

    INPUT_BYTE( cinfo, c, return FALSE );
    INPUT_BYTE( cinfo, c2, return FALSE );
    if ( ( c != 0xFF ) || ( c2 != (int) M_SOI ) ) {
        ERREXIT2( cinfo, JERR_NO_SOI, c, c2 );
    }

    cinfo->unread_marker = c2;

    INPUT_SYNC( cinfo );
    return TRUE;
}


/*
 * Read markers until SOS or EOI.
 *
 * Returns same codes as are defined for jpeg_consume_input:
 * JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI.
 */

METHODDEF int
read_markers( j_decompress_ptr cinfo ) {
    /* Outer loop repeats once for each marker. */
    for (;; ) {
        /* Collect the marker proper, unless we already did. */
        /* NB: first_marker() enforces the requirement that SOI appear first. */
        if ( cinfo->unread_marker == 0 ) {
            if ( !cinfo->marker->saw_SOI ) {
                if ( !first_marker( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
            } else {
                if ( !next_marker( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
            }
        }
        /* At this point cinfo->unread_marker contains the marker code and the
         * input point is just past the marker proper, but before any parameters.
         * A suspension will cause us to return with this state still true.
         */
        switch ( cinfo->unread_marker ) {
            case M_SOI:
                if ( !get_soi( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            case M_SOF0:/* Baseline */
            case M_SOF1:/* Extended sequential, Huffman */
                if ( !get_sof( cinfo, FALSE, FALSE ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            case M_SOF2:/* Progressive, Huffman */
                if ( !get_sof( cinfo, TRUE, FALSE ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            case M_SOF9:/* Extended sequential, arithmetic */
                if ( !get_sof( cinfo, FALSE, TRUE ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            case M_SOF10:/* Progressive, arithmetic */
                if ( !get_sof( cinfo, TRUE, TRUE ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

                /* Currently unsupported SOFn types */
            case M_SOF3:/* Lossless, Huffman */
            case M_SOF5:/* Differential sequential, Huffman */
            case M_SOF6:/* Differential progressive, Huffman */
            case M_SOF7:/* Differential lossless, Huffman */
            case M_JPG: /* Reserved for JPEG extensions */
            case M_SOF11:/* Lossless, arithmetic */
            case M_SOF13:/* Differential sequential, arithmetic */
            case M_SOF14:/* Differential progressive, arithmetic */
            case M_SOF15:/* Differential lossless, arithmetic */
                ERREXIT1( cinfo, JERR_SOF_UNSUPPORTED, cinfo->unread_marker );
                break;

            case M_SOS:
                if ( !get_sos( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
                cinfo->unread_marker = 0;/* processed the marker */
                return JPEG_REACHED_SOS;

            case M_EOI:
                TRACEMS( cinfo, 1, JTRC_EOI );
                cinfo->unread_marker = 0;/* processed the marker */
                return JPEG_REACHED_EOI;

            case M_DAC:
                if ( !get_dac( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            case M_DHT:
                if ( !get_dht( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            case M_DQT:
                if ( !get_dqt( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            case M_DRI:
                if ( !get_dri( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            case M_APP0:
            case M_APP1:
            case M_APP2:
            case M_APP3:
            case M_APP4:
            case M_APP5:
            case M_APP6:
            case M_APP7:
            case M_APP8:
            case M_APP9:
            case M_APP10:
            case M_APP11:
            case M_APP12:
            case M_APP13:
            case M_APP14:
            case M_APP15:
                if ( !( *cinfo->marker->process_APPn[cinfo->unread_marker - (int) M_APP0] )( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            case M_COM:
                if ( !( *cinfo->marker->process_COM )( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            case M_RST0:/* these are all parameterless */
            case M_RST1:
            case M_RST2:
            case M_RST3:
            case M_RST4:
            case M_RST5:
            case M_RST6:
            case M_RST7:
            case M_TEM:
                TRACEMS1( cinfo, 1, JTRC_PARMLESS_MARKER, cinfo->unread_marker );
                break;

            case M_DNL: /* Ignore DNL ... perhaps the wrong thing */
                if ( !skip_variable( cinfo ) ) {
                    return JPEG_SUSPENDED;
                }
                break;

            default:    /* must be DHP, EXP, JPGn, or RESn */
                /* For now, we treat the reserved markers as fatal errors since they are
                 * likely to be used to signal incompatible JPEG Part 3 extensions.
                 * Once the JPEG 3 version-number marker is well defined, this code
                 * ought to change!
                 */
                ERREXIT1( cinfo, JERR_UNKNOWN_MARKER, cinfo->unread_marker );
                break;
        }
        /* Successfully processed marker, so reset state variable */
        cinfo->unread_marker = 0;
    } /* end loop */
}


/*
 * Read a restart marker, which is expected to appear next in the datastream;
 * if the marker is not there, take appropriate recovery action.
 * Returns FALSE if suspension is required.
 *
 * This is called by the entropy decoder after it has read an appropriate
 * number of MCUs.  cinfo->unread_marker may be nonzero if the entropy decoder
 * has already read a marker from the data source.  Under normal conditions
 * cinfo->unread_marker will be reset to 0 before returning; if not reset,
 * it holds a marker which the decoder will be unable to read past.
 */

METHODDEF boolean
read_restart_marker( j_decompress_ptr cinfo ) {
    /* Obtain a marker unless we already did. */
    /* Note that next_marker will complain if it skips any data. */
    if ( cinfo->unread_marker == 0 ) {
        if ( !next_marker( cinfo ) ) {
            return FALSE;
        }
    }

    if ( cinfo->unread_marker ==
        ( (int) M_RST0 + cinfo->marker->next_restart_num ) ) {
        /* Normal case --- swallow the marker and let entropy decoder continue */
        TRACEMS1( cinfo, 2, JTRC_RST, cinfo->marker->next_restart_num );
        cinfo->unread_marker = 0;
    } else {
        /* Uh-oh, the restart markers have been messed up. */
        /* Let the data source manager determine how to resync. */
        if ( !( *cinfo->src->resync_to_restart )( cinfo,
                                                  cinfo->marker->next_restart_num ) ) {
            return FALSE;
        }
    }

    /* Update next-restart state */
    cinfo->marker->next_restart_num = ( cinfo->marker->next_restart_num + 1 ) & 7;

    return TRUE;
}


/*
 * This is the default resync_to_restart method for data source managers
 * to use if they don't have any better approach.  Some data source managers
 * may be able to back up, or may have additional knowledge about the data
 * which permits a more intelligent recovery strategy; such managers would
 * presumably supply their own resync method.
 *
 * read_restart_marker calls resync_to_restart if it finds a marker other than
 * the restart marker it was expecting.  (This code is *not* used unless
 * a nonzero restart interval has been declared.)  cinfo->unread_marker is
 * the marker code actually found (might be anything, except 0 or FF).
 * The desired restart marker number (0..7) is passed as a parameter.
 * This routine is supposed to apply whatever error recovery strategy seems
 * appropriate in order to position the input stream to the next data segment.
 * Note that cinfo->unread_marker is treated as a marker appearing before
 * the current data-source input point; usually it should be reset to zero
 * before returning.
 * Returns FALSE if suspension is required.
 *
 * This implementation is substantially constrained by wanting to treat the
 * input as a data stream; this means we can't back up.  Therefore, we have
 * only the following actions to work with:
 *   1. Simply discard the marker and let the entropy decoder resume at next
 *      byte of file.
 *   2. Read forward until we find another marker, discarding intervening
 *      data.  (In theory we could look ahead within the current bufferload,
 *      without having to discard data if we don't find the desired marker.
 *      This idea is not implemented here, in part because it makes behavior
 *      dependent on buffer size and chance buffer-boundary positions.)
 *   3. Leave the marker unread (by failing to zero cinfo->unread_marker).
 *      This will cause the entropy decoder to process an empty data segment,
 *      inserting dummy zeroes, and then we will reprocess the marker.
 *
 * #2 is appropriate if we think the desired marker lies ahead, while #3 is
 * appropriate if the found marker is a future restart marker (indicating
 * that we have missed the desired restart marker, probably because it got
 * corrupted).
 * We apply #2 or #3 if the found marker is a restart marker no more than
 * two counts behind or ahead of the expected one.  We also apply #2 if the
 * found marker is not a legal JPEG marker code (it's certainly bogus data).
 * If the found marker is a restart marker more than 2 counts away, we do #1
 * (too much risk that the marker is erroneous; with luck we will be able to
 * resync at some future point).
 * For any valid non-restart JPEG marker, we apply #3.  This keeps us from
 * overrunning the end of a scan.  An implementation limited to single-scan
 * files might find it better to apply #2 for markers other than EOI, since
 * any other marker would have to be bogus data in that case.
 */

GLOBAL boolean
jpeg_resync_to_restart( j_decompress_ptr cinfo, int desired ) {
    int marker = cinfo->unread_marker;
    int action = 1;

    /* Always put up a warning. */
    WARNMS2( cinfo, JWRN_MUST_RESYNC, marker, desired );

    /* Outer loop handles repeated decision after scanning forward. */
    for (;; ) {
        if ( marker < (int) M_SOF0 ) {
            action = 2;
        }               /* invalid marker */
        else if ( marker < (int) M_RST0 || marker > (int) M_RST7 ) {
            action = 3;
        }               /* valid non-restart marker */
        else {
            if ( marker == ( (int) M_RST0 + ( ( desired + 1 ) & 7 ) ) ||
                marker == ( (int) M_RST0 + ( ( desired + 2 ) & 7 ) ) ) {
                action = 3;
            }       /* one of the next two expected restarts */
            else if ( marker == ( (int) M_RST0 + ( ( desired - 1 ) & 7 ) ) ||
                     marker == ( (int) M_RST0 + ( ( desired - 2 ) & 7 ) ) ) {
                action = 2;
            }       /* a prior restart, so advance */
            else {
                action = 1;
            }       /* desired restart or too far away */
        }
        TRACEMS2( cinfo, 4, JTRC_RECOVERY_ACTION, marker, action );
        switch ( action ) {
            case 1:
                /* Discard marker and let entropy decoder resume processing. */
                cinfo->unread_marker = 0;
                return TRUE;

            case 2:
                /* Scan to the next marker, and repeat the decision loop. */
                if ( !next_marker( cinfo ) ) {
                    return FALSE;
                }
                marker = cinfo->unread_marker;
                break;
            case 3:
                /* Return without advancing past this marker. */
                /* Entropy decoder will be forced to process an empty segment. */
                return TRUE;
        }
    } /* end loop */
}


/*
 * Reset marker processing state to begin a fresh datastream.
 */

METHODDEF void
reset_marker_reader( j_decompress_ptr cinfo ) {
    cinfo->comp_info = NULL;    /* until allocated by get_sof */
    cinfo->input_scan_number = 0;   /* no SOS seen yet */
    cinfo->unread_marker = 0;   /* no pending marker */
    cinfo->marker->saw_SOI = FALSE; /* set internal state too */
    cinfo->marker->saw_SOF = FALSE;
    cinfo->marker->discarded_bytes = 0;
}


/*
 * Initialize the marker reader module.
 * This is called only once, when the decompression object is created.
 */

GLOBAL void
jinit_marker_reader( j_decompress_ptr cinfo ) {
    int i;

    /* Create subobject in permanent pool */
    cinfo->marker = (struct jpeg_marker_reader *)
                    ( * cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_PERMANENT,
                                                  SIZEOF( struct jpeg_marker_reader ) );
    /* Initialize method pointers */
    cinfo->marker->reset_marker_reader = reset_marker_reader;
    cinfo->marker->read_markers = read_markers;
    cinfo->marker->read_restart_marker = read_restart_marker;
    cinfo->marker->process_COM = skip_variable;
    for ( i = 0; i < 16; i++ ) {
        cinfo->marker->process_APPn[i] = skip_variable;
    }
    cinfo->marker->process_APPn[0] = get_app0;
    cinfo->marker->process_APPn[14] = get_app14;
    /* Reset marker processing state */
    reset_marker_reader( cinfo );
}
